1. Field of Invention
This invention relates generally to wrist pads associated with a keyboard or other computer input device, and more particularly to a wrist pad which incorporates a pressure-sensitive switch and serves to generate a warning signal when a wrist of the operator whose hand manipulates the input device applies pressure thereto.
2. Status of Prior Art
Repetitive strain injury (RSI) is defined in the text "Repetitive Strain Injury--A Computer Users' Guide" whose principal author is Dr. Emil Pascarelli, as a cumulative trauma disorder (CTD). This disorder stems from prolonged repetitive, forceful or awkward hand movements. When these hand movements are accompanied by poor posture as well as a heavy workload, the stage is then set for RSI, a serious injury that can cause pain, weakness, numbness or impairment of motor control.
According to the U.S. Department of Labor, RSI accounts for about 60 percent of all job-related injuries. The concern of the present invention is with RSI resulting from the manual operation of an input device associated with a computer, such as a keyboard or a mouse.
A computer keyboard functions to enter alpha-numerical data into the computer. A mouse is a hand-held, button-operated input device which when rolled along a flat surface, then directs a cursor to move correspondingly about a computer screen, thereby allowing the operator to select particular operations or manipulate text and graphics. It is predicted that in the year 2000, three quarters of all jobs in the United States will probably require the use of a computer. It is for this reason that public schools throughout the country are now teaching students how to operate computers. It is an almost universal practice among computer users, when operating a keyboard or mouse, to rest the wrists of the hands on the edge of the work surface on which the input device is placed, or on a cushioned wrist pad in front of the keyboard or mouse.
Wrist supporting pads for computer operators give rise to dorsiflexion. Dorsiflexion refers to a hand bending upwardly at the wrist. Continual dorsiflexion which takes place when typing with the wrist resting on a wrist pad is a recognized major cause of RSI. Most computer guides therefore instruct operators to assume a proper typing posture by having the wrists float above the wrist pad and to rest the wrists only while not typing. But while this wrist posture is recommended by computer guides, no means have heretofore been available to facilitate proper wrist posture.
The 1995 patent to Hart U.S. Pat. No. 5,445,349 discloses a wrist rest formed by a cloth sack filled with rice. This sack is engaged by the wrist of an operator typing on a computer keyboard to relieve the physical stress occasioned by this activity. The 1994 patent to Martin et al. U.S. Pat. No. 5,340,067 discloses a cushioned pad for supporting the wrist of a computer mouse operator. In both of these patents, dorsiflexion takes place, and these wrist rests with continued use are therefore likely to give rise to RSI.
The 1989 U.S. Pat. No. 4,807,642 to Brown calls attention to musculoskeletal pain resulting from RSI and its serious consequences. Brown provides a monitoring device for detecting muscle strain which might lead to RSI. This monitoring device supplies the worker with biofeedback, serving to induce the worker to try out different work methods and thereby determine which one of these methods produces the least amount of tension. But Brown fails to recognize the role of proper wrist posture in operating a computer input device, and he discloses no means to induce a worker to maintain a proper wrist posture.
The 1994 Daneshvar U.S. Pat. No. 5,374,018 illustrates a soft pad for a computer keyboard adapted to support the palm or wrist of the operator. As previously noted, a pad on which an operator rests his wrists as he types on a keyboard with his hands result in dorsiflexion, and this may in time lead to repetitive strain injury.
Conner in his 1992 U.S. Pat. No. 5,165,630 provides a pad for a computer mouse which serves to elevate the wrist of the operator to reduce stress on the tendons controlling the wrist and hand. But as pointed out above, the ideal posture for the wrist of the user of a computer input device is one in which the wrist floats or hovers above a wrist pad, and makes no contact therewith. This is not achieved by the Conner pad.
Inasmuch as the invention resides in a pressure-sensitive wrist pad for use with a computer input device to provide a warning signal only when the wrist of an operator presses against the pad, of prior art background interest is the 1989 patent to Sugarman U.S. Pat. No. 4,858,620. This patent discloses a warning system that includes pressure sensors to sense the pressure of a foot against a cast and to provide a warning signal when this pressure reaches a dangerous level. The 1985 Kress U.S. Pat. No. 4,554,930 provides pressure sensors for measuring the pressure between the skin and a rest surface, which pressure, if excessive, may cause ulcers.